Explosionproof conduit outlet box and switch unit



Oct. 23, 1934. R OLLEY 1,977,891

EXPLOSIONPROOF CONDUIT OUTLET BOX AND SWITCH UNIT Filed Dec. 15, 1933 2 SheetsSheet l INVENTOR.

ATTORNEYS.

Oct. 23, 1934. R H OLLEY 1,977,891

EXPLOSIONPROOF CONDUIT OUTLET BOX AND SWITCH UNIT Eiled Dec. 15, 1933 2 Sheets-Sheet 2 INVENTORY ATTORNEYS.

Patented oct. '23, 1934 PATENT OFFICE EXPLOSIONPROOF CONDUIT OUTLET BOX AND SWITCH UNIT Raymond H. Olley, Syracuse, N. Y., assignor to Grouse-Hinds Company, Syracuse, N. Y., a corporation of New York Application December 15, 1933, Serial No. 702,553

7 Claims.

This invention relates to explosion proof electric conduit outlet boxes, and has for its object a particularly simple and efficient explosion proof means by which electric appliances, as switches, can; be readily applied to standard outlet boxes interchangeably with the explosion proof covers for said boxes, and more particularly, a construction whereby the switch unit, that is, the switch and .its support canbe applied to the box and 10 located in the desired position or angle in the box and thereafter the cap, which is interchangeable with the standard cover, applied to both the switch support and the box, while the switch support is assembled with and supported by the box. 16 By explosion proof is meant, a structure by which explosions occurring within the box are confined in the box. Explosions are liable to occur where there are explosive vapors, as gasoline vapors, in the surrounding atmosphere.

' 20 It will be understoodithat explosion proof electricalfixtures are so constructed that should an explosion occur within the fixture, theignited gases will be cooled before they escape below the ignition point of the explosive gases in the surrounding atmosphere. It is common practice to attain this end in regard to joints between the various elements of the fixture by accurately grinding the surfaces of the joints, whereby there is a minimumof space at the joints between'the .various elements so that there is a very small or thin passage for the ignited gases to escape, and hence, a comparatively small amount of ignited gases comes in contact with the maximum cooling surface of the metal when escaping. How- .ever, the grounding operation increases the cost of the fitting and due to expansion and contraction, and the natural tendency of the iron to warp, these joints, when ground accurate at the factory very often lose their accuracy in a comparatively short time with the result that the joint is no longer effective to adequately cool the escaping gases. Therefore, in the illustrated embodiment' of my invention, I have shown threaded joints which form long tortuous paths for the escape of ignited gases, giving them ample cooling surface to come in contact with before escaping to the surrounding atmosphere. This feature in its broader aspect forms nopart of this invention, but is the subject mater of my pending application Serial No. 681,160, filed July, 19, 1933.

The subject matter'of this application is the mounting or assembling of the switch'support in uthe box, as a unit, before the threaded cap is applied, so that the switch unit can be mounted in any one of a number of radial positions in the box, and the cap when applied or screwed on the switch support and the collar on the box, does not turn the switch unit or any part thereof and upset the original location thereof, and further, so that no positioning or adjustment is necessary after the cap has be-en'applied.

The invention consists in the novel features and in the combinations and constructions hereinafter set forth and claimed.

In describing this invention, reference is had to the accompanying drawings in which like characters designate corresponding parts in all the views.

Figure 1 is an exploded isometricview, partly in section, of a conduit outlet box and switch unit embodying my invention.

Figure 2 is a transverse sectional View through the conduit outlet box and switch unit.

This invention comprises, generally, a conduit outlet box provided Withan externally threaded collar on one side thereof enclosing an opening to the interiorof thebo-x, a switch and a switch support extending or depending into the box and including an externally threaded head projecting above the upper edge of the collar and supported on the collar, preferably by resting on the outer edge thereof, the switch having an operating member or members exposed on the outer face of thehead and a cap threading on the head and the collar, the collar and the switch support having coacting means for holding the switch support from turning movement during the threading of the cap on the collar and the head or during turning movement of the cap relative to the collar and the switch support when assembled, the threaded surfaces of the collar and the head and of the cap being so located that the cap threads on the collar and the head at the same time.

1 designates the conventional conduit outlet box having an internally threaded cylindrical flange 2 on one side thereof confining an entrance opening into the box, the flange receiving the threads of the cover. The box is also provided with one or more nipples 3 for connection in the electric conduit system enclosing the service wires.

4 designates an externally threaded collar threading into the flange 2 and interchangeable with the usual cover, which threads into the flange 2, this being an adapter for applying a switch unit to the switch box. As there is no shoulder or anything for the collar to bottom on when threadedinto the flange 2, means is provided for limiting the threading of the collar 4 into the flange 2, this means being shown as a snap ring 5, placed in its desired location on the collar' so as to coact with the upper edge of the flange 2 or a beveled surface 6 at the upper edge of the flange 2 and to limit the inward threading movement of the collar 4.

7 designates the switch unit including a switch and a switch support and operating means for the switch. 8 designates generally the switch, which may be of any suitable form, size and construction, it being here shown as of the push button type and having a pair of push buttons, one of which is shown at 9. The switch support includes a head 10 and a suitable frame or yoke 11 depending from the inner side of the head and to which the switch is secured, as by screws 12. The yoke is secured to the head in any suitable manner, as by screws 13.

14 designates an operating member for the switch or for the push buttons thereof, there being two of such operating members, as the switch is of the two push button type. These operating members slidably tit passages extending through the head and have heads or push buttons 15' at their upper ends operable from the outer side of the head.

The: head 10 is discoidal or cylindrical in general form and has its periphery threaded. The head is of less diameter than: the external diameter of thecoll'ar4 and. of greater diameter than the internal diameter of the collar 4- so that the head rests upon the upper or outer edge of the collar 4.

The means fonholding the switch unit from turning relatively to the collar 4, particularly while the cap to be presently described is being threaded on or off the collar 4 and the head, consists of interlocking means on the switch unit and the upper edge of the collar 4 and as here illustrated, the upper edge of the collar 4 is notched at 16, practically throughout its entire extent, so that the upper edge is castellated. The switch support is formed with projections 1'? for entering the notches l6, these projections being provided at the ends: of the portions of the yoke 11 overlying the inner side of thehead- 10. Although only two diametrically opposite notches are required to locate the head 1c in any annular or radial positionrelative to the collar 4, a plurality of such notches are provided in order togive a wide choice in regard to the angular position of the switch in. the box.

1.8 designates the cap, although in this embodiment of my inventionthe cap is shown'without a head or a bottom: andis practically a sleeve, The cap 1.8]is provi'dedwith two sets of threads 19 and 2.0 in the outer and. inner end portions thereof, the threaded surface 19 being of less diameter than the threaded surface 20 and the threads 19 thread on the head 10 while the threads 20 thread. on the collar 4. Also", an internal. shoulder 21 is provided on the capbetween the threaded portions which is opposed to the upper edge of the collar 4.. The-threads of the head and of the collar 4 are of the same pitch, and'owing to the relativelocation of the head 10 and the collar 4 and of the cap 18, the threads 2U thread on the collar 4 at the same time that the threads 19 are threading on the head 10'. The threaded connection. provides a: joint having a combined axial and rotary movement to engage and disengageit and any equivalent joint may be substituted, as something in the nature of a bayonet joint.

In operation, the wires in the outlet box are pulled out slightly and. attached to the binding terminals of. the switch and the switch unit, including the head 10, applied to the box through the collar 4 and located in the desired radial angle by placing the projections 17 in any two diametrically opposite notches 16. The head 10 then rests on the upper edge of the collar 4. The cap 18 is then applied, the threads 20 turning on the collar 4 at the same time that the threads 19 are turning on the head 10. By reason of. the threaded joints between the collar and cap and between the cap and the head, long tortuous paths of large capacity are provided in a simple manner for cooling the hot exploded gases.

Although theada-pter collar 4 is shown as applied to the conduit outlet box, nevertheless, it

Lid

will be apparentthat the box may be initially formed with the collar integral therewith. WhatI claim is:

1. An electric conduit outlet box provided with an externally threaded collar on one side thereof enclosing an opening to the interior of the box, a switch and a switch support extending into the box through'thecollar and including an externally threaded head projecting above the upper edge or the collar and supported by the collar, the switch; having an operating member exposed on the outer faceof the head and a cap threading on the head and. the collar, the collar and switch supporthaving. coacting means for holding the. switch support including the head from turning movement during the threading oi the cap on. the collar and the head. H

2;. Am electricconduit outlet box provided with an externally" threaded collar on one side thereof. enclosing. an opening to: theinteriorot the box, a switch and a switch support extending into the box through the collar and including anexternallythreaded head projecting above the upper edge of thezcollar, said. switch support and collar having coacting meansto carry the switch support and hold it from turning movement and the switch. having an operating member extending through the head and. exposed. on the upper face .otthe: head. and an internally threaded cap havtwo sets of threads-arranged to thread simuttaneously on the collar and. on. the head.

3.. An. electric outlet box provided: with a threaded. collaron one sidethereofi and enclosingan opening to the interior-vet the box," a

switch. and a switch support-extendmg through the collarintc! the box and including an. externally threaded head projecting abovetheupper edge of'the collar and resting at its margin on. the upper edge of the collar, said collar having its upper edge notched and. the switchsupport having. projections for entering a notch or notches of the col lar to hold the switch support from turning movement and. an internally threaded cap threading onzthe' collar and the'head.

4-. electric conduit outlet box provided with anexternally threaded collar on o-ne side thereof and enclosing anopening. to the interior'of the box, a switch and. a switch support extending into, thebox through the collar and including anexternally threaded head et less diameter than the'extemal. diameter of the collanthe switch support and the collar having enacting means for' holding. the switch support from turning movemerit, the switch having: an operating member extending throughthe head and operable from the outerside thereofand a cap having: two'setsof threads on the inner face thereoi for threading simultaneously on; the collar and'the: head '5. An electric con'duit'outlet box provided with an externally threaded collar on one side thereof andenclosing: an opening to the interior of the box; aswitch and. a switch support extending fio into the box through the collar and including an externally threaded head of less diameter than the external diameter of the collar, the switch support and the collar having coacting means for holding the switch support from turning movement, the switch having an operating member extending through the head and operable from the outer side thereof and a cap having two sets of threads on the inner face thereof for threading simultaneously on the collar and the head, the cap also having a shoulder between the two sets of threads for coacting with the upper edge of the collar.

6. An electric conduit outlet box provided with an externally threaded collar on one side thereof enclosing an opening to the interior of the box, and a switch and a switch support extendinginto the box through the collar and including an externally threaded collar projecting above the upper edge of the collar, the switch support and the collar having coacting means for supporting the switch support and holding it from turning movement relatively to the collar and the head being of less diameter than the external diameter of the collar and a cap having its end portions internally threaded, the outer end portion threading on the head and the inner end portion on the collar, the outer end portion being of less diameter than the inner end portion, whereby the cap threads simultaneously on the collar and on the head.

7. An electric conduit outlet box provided with an externally threaded collar on one side thereof enclosing an opening to the interior of the box, a switch and a switch support extending into the box through the collar and including an externally threaded head of less diameter than the outside diameter of the collar, whereby the head rests on the edge of the collar, the collar having its upper edge notched and the switch support being provided with projections for interlocking in the notches to hold the switch support from turning movement relatively to the collar and a cap having an outer end portion of less diameter than its inner end portion, and said portions being internally threaded and the outer end portion threading on the head and the inner end portion on the collar, the cap being also formed with an internal annular shoulder between the threaded end portions for engaging the upper edge of the collar.

, RAYMOND H. OLLEY. 

